Chich expression correctly describes force using Sl units

Regarding the history of the universe, which of the following is true? Regarding the history of the universe, which of the follo

ale4655 [162]

Explanation:

1. The universe consisted of hydrogen and helium initially. This statement is true.

2. It is important to understand radioactive decay in order to understand this question, here's a good analogy:

A snake will shed it's skin, just as an atom will shoot off different parts of itself. It would be very difficult to force that snake to reenter it's skin once it sheds, just as it takes a lot of energy to force <em>fusion</em><em> </em>of atoms and the parts mentioned. In normal circumstances, nuclear decay is one-way.

3. The earth is a giant floating rock in space. It took many many years to gather a bunch of asteroids and dust to make this planet.

4. I shouldn't have to explain this one, it doesn't make much sense.

5 0

3 years ago

Determine the launch speed of a horizontally launched cannonball that lands 26.3

nlexa [21]

Answer:

The cannon has an initial speed of 13.25 m/s.

Explanation:

The launched cannonball is an example of a projectile. Thus, its launch speed can be determined by the application of the formula;

R = u $\sqrt{\frac{2H}{g} }$

Where: R is the range of the projectile, u is its initial speed, H is the height of the cliff and g is the gravitaty.

R = 26.3 m, H = 19.3 m, g = 9.8 m/ $s^{2}$ .

So that:

26.3 = u $\sqrt{\frac{2*19.3}{9.8} }$

$(26.3)^{2}$ = $u^{2}$ x $\frac{38.6}{9.8}$

691.69 = $u^{2}$ x $\frac{38.6}{9.8}$

$u^{2}$ = $\frac{691.69*9.8}{38.6}$

= $\frac{6778.562}{38.6}$

$u^{2}$ = 175.6104

⇒ u = $\sqrt{175.6104}$

= 13.2518

u = 13.25 m/s

The initial speed of the cannon is 13.25 m/s.

4 0

3 years ago

an athlete runs 300 m up a hill at a steady speed of 3.0 m/s. She then immediately runs the same distance at 6.0 m/s . What is h

mina [271]

Answer:

4.0 m/s

Explanation:

In the first part of the run, the athlete runs a distance of

$d_1 = 300 m$

at a speed of

$v_1 = 3.0 m/s$

So, the time he/she takes is

$t_1 = \frac{d_1}{v_1}=\frac{300}{3.0}=100 s$

In the second part of the run, the athlete covers an additional distance of

$d_2 = 300 m$

with a speed

$v_2 = 6.0 m/s$

So, the time taken in this second part is

$t_2 = \frac{d_2}{v_2}=\frac{300}{6.0}=50 s$

So, the total distance covered is

d = 300 m + 300 m = 600 m

And the total time taken

t = 100 s + 50 s = 150 s

Therefore, the average speed for the entire trip is

$v=\frac{d}{t}=\frac{600}{150}=4.0 m/s$

4 0

4 years ago

The outside diameter of the playing area of an optical Blu-ray disc is 11.75 cm, and the inside diameter is 4.50 cm. When viewin

erica [24]

Answer:

The minimum angular speed 57.0 rad/s

Explanation:

In this exercise we must use the relationships between the angular and linear magnitudes, for the speeds we have

v = w r

As they give us that linear velocity is constant, we will calculate the angular velocity for the two radii, external and internal

r1 = 11.75 cm (1 m / 100cm) = 0.1175 m

w1 = v / r1

w1 = 6.70 / 0.1175

w1 = 57.0 rd / s

R2 = 4.50 cm = 0.0450 m

w2 = 6.70 / 0.0450

w2 = 148 rad / s

The minimum angular speed 57.0 rad / s

4 0

3 years ago

What is the energy (in evev) of a photon of visible light that has a wavelength of 500 nmnm?

lisabon 2012 [21]

<h3>Answer:</h3>

E≈2,5 eV

<h3>Explanation:</h3>

_______________

λ=500 nm = 500·10⁻⁹ m

c=3·10⁸ m/s

h=6,63·10⁻³⁴ J·s = 4,14·10⁻¹⁵ eV·s

_______________

E - ?

_______________

$\displaystyle \boldsymbol{E}=h\nu =h \frac{c}{\lambda} =4,14\cdot 10^{-15} \; eV\cdot s\cdot \; \frac{3\cdot 10^8\; m/s}{500\cdot 10^{-9}\; m} =2,484\; eV\approx \boldsymbol{2,5\; eV}$

6 0

2 years ago